CARDOZO, J.

In July, 1916, there was a strike of motormen and conductors on the street railroad operated by the defendant in the city of New York. The Washington Detective Bureau undertook to furnish other motormen and conductors, and also guards or watchmen to protect the passengers and cars from violence. One of these guards was the plaintiff. He was injured in a collision as the result of the defendant's negligence. The question is whether his relation to the defendant at the time of the collision was that of an employee to an employer, either general or special ( Matter of DeNoyer v. Cavanaugh, 221 N.Y. 273; Matter of Schweitzer v. Thompson Norris Co., 229 N.Y. 97.) If it was, the remedy under the Workmen's Compensation Law (Consol. Laws, chap. 67), is exclusive of every other. If it was not, the common-law remedy for negligence survives. The plaintiff had a verdict at Trial Term. The Appellate Division reversed and dismissed the complaint.

Beyond doubt, the detective bureau was the plaintiff's general employer. ( Matter of DeNoyer v. Cavanaugh supra.) It hired him and paid him and had the power to discharge him. He was not told by the men who hired him of the nature of the arrangement between the bureau and the railroad. All that he was told was that they were sending him to guard cars, just as they had sent him on other occasions to guard factories or offices. On his arrival at the barn, he found one of the employees of the bureau giving orders to the watchmen, and assigning them to duty. Under orders thus given, he went upon a car, and, while guarding it, was injured.

We see nothing in these facts which was equivalent as matter of law to the acceptance of a change of masters. We do not doubt that the same man may be in the general employment of one master and the special employment of another ( Matter of Schweitzer v. Thompson Norris Co., supra; McNamara v. Leipzig, 227 N.Y. 291). But employment, like any other contract, presupposes understanding. The new relation cannot be thrust upon the servant without knowledge or consent ( McNamara v. Leipzig, supra; Standard Oil Co. v. Anderson, 212 U.S. 215, 221; Hull v. Phila. Reading Ry. Co., 252 U.S. 475.) He must understand that he is submitting himself to the control of a new master. We are not concerned at the moment with cases in which the rights of third persons are involved. We speak of cases where the parties to the disputed relation are the parties to the controversy. Understanding may be inferred from circumstances, but understanding there must be. Common-law rights and remedies are not lost by stumbling unawares into a new contractual relation. There can be no unwitting transfer from one service to another.

If understanding of a new relation may be imputed to the plaintiff, it is at most an inference of fact to be drawn by a jury. Nothing in the situation as he knew it made the inference inevitable. He is not chargeable with the legal consequences of the arrangement between the bureau and the railroad as actually made. He is chargeable only with the legal consequences of the arrangement as known and approved. Knowledge and approval may be inferred where the servant, continuing in the service, takes his orders from some one other than the hirer or the hirer's representative. Here the hirer's representative was, or seemed to be, in continuous authority. A detective agency may undertake to guard the property of another with its own men and in its own way ( Standard Oil Co. v. Anderson, 212 U.S. 215, 221; McNamara v. Leipzig, supra; Matter of Schweitzer v. Thompson Norris Co., supra). It may undertake, on the other hand, to furnish another with men so that he may guard his property for himself ( Standard Oil Co. v. Anderson; McNamara v. Leipzig, supra). In the one undertaking, the relation of employment is unchanged. In the other, a new relation arises when the transfer is effected and the contract is fulfilled. Whether this undertaking fell in the one class or in the other, the plaintiff did not know. He remained, in default of knowledge, the servant of the hirer.

The judgment of the Appellate Division should be reversed, and that of the Trial Term affirmed, with costs in the Appellate Division and in this court.

HISCOCK, Ch. J., CHASE, COLLIN, POUND, CRANE and ANDREWS, JJ., concur.

Judgment accordingly.